Body mass index and physical function in older women

We modified existing standardized measurement tools in the Physical Performance Test and tasks from the Frailty and Injuries: Cooperative Studies of Intervention Technique Study to evaluate physical function in older women. Our objectives were (1) to characterize physical function themes based on combinations of tasks (deriving factors or components) and (2) to quantify the correlation between derived factors and body mass index (BMI).

Nutrition risk screens from enrollees in a Medicare-managed risk program served as the sampling frame. To obtain adequate representation for a range of BMI, a random sample was obtained of 90 women from the following BMI strata: BMI, 22 to <27 kg/m(2); BMI, 27 to <30 kg/m(2); and BMI, > or =30 kg/m(2). Subjects were asked to perform a series of 18 functional tasks during a home visit.

The mean age was similar in the three BMI groups with an overall mean age of 71 +/- 4.9 years (SD). Factors characterized by lower-body function, upper-body function, coordination, and strength were responsible for 30%, 11%, 9%, and 9% of the variance in task scores, respectively. BMI, controlling for age, explained 5%, 14%, 3%, and 0% of the variation in these factors, respectively. Higher BMI is associated significantly with poorer upper- and lower-body function but is not associated significantly to strength or coordination.

Higher BMI seems to differentially impede specific aspects of physical function, especially upper-body function, and to a lesser extent, lower-body function. BMI does not seem to be associated with levels of coordination or strength. Better understanding of how BMI impacts physical function will aid in the design of interventions to promote independent living in elderly, obese women.